1. Field of the Invention
The present invention relates to an imprint apparatus and an article manufacturing method using the same.
2. Description of the Related Art
As the demand for microfabrication of semiconductor devices increases, not only a conventional photolithography technology but also a microfabrication technology in which a mold and an uncured resin on a substrate are pressed against each other to thereby form a resin pattern, which corresponds to the fine concave and convex pattern formed on the mold, on the substrate exist. This technology is also referred to as an “imprint technology”, by which a fine structure with dimensions of a few nanometers can be formed on the substrate. One example of imprint technologies includes a photo-curing method. The photo-curing method first applies an ultraviolet curable resin (imprint resin, photocurable resin) to the shot area (imprint area) on the substrate. Next, the resin (uncured resin) and a mold are pressed against each other. After the ultraviolet curable resin is irradiated with ultraviolet light for curing, the cured resin is released from the mold, whereby a resin pattern is formed on the substrate.
In the conventional imprint apparatus employing the aforementioned technique, air bubbles may be entrapped in a resin pattern-forming unit when a mold is pressed against a resin on a substrate. When the resin is cured with entrapped air bubbles, defects may occur on the pattern to be formed. In order to avoid such a pattern defect, U.S. Patent Publication No. 2007/0114686 discloses a method for discharging gas between a substrate and a mold in which the mold is temporarily deflected toward the substrate in a convex shape, a resin on the substrate is pressed against the mold in this state, and the mold is then restored to a flat surface so as to press the entire pattern surface against the resin. According to the method, gas present between a mold and a resin may be expelled to the outside, and thus, air bubbles entrapped in a resin may be reduced. Furthermore, Japanese Patent Laid-Open No. 2009-532245 discloses an apparatus that depressurizes a space between a mold and a substrate to thereby reduce the remaining entrapped air bubbles.
Furthermore, in the conventional imprint apparatus, if the entire surface of the mold is peeled off from the cured resin, at which an imprinting operation was performed, at the same time upon mold releasing, a large peel-off stress may be instantaneously applied at the interface (contact portion) between the mold and the cured resin. This stress may lead to the distortion of a pattern to be formed, resulting in a pattern defect. In contrast, in the method disclosed in U.S. Patent Publication No. 2007/0114686, a mold is temporarily deformed in a manner similar as mentioned above and the mold is gradually peeled off from the periphery of a cured resin pattern-forming unit upon the release of the mold, whereby the occurrence of a sharp stress may be avoided.
However, when a mold is deformed and released from the periphery of the resin pattern as in the method disclosed in U.S. Patent Publication No. 2007/0114686, the resin pattern is inclined by being pushed by the concave and convex pattern of a deflected mold, and thus, a stress occurs on the root portion thereof. When the stress becomes larger than a resin plastic stress, the resin pattern is kept inclined and may not be restored back to its original shape. Furthermore, in the mold disclosed in U.S. Patent Publication No. 2007/0114686, the portion including the concave and convex pattern is made thin so as to be readily deflected. In this case, the mold is largely deformed upon the release of the mold, and thus, the inclination of the resin pattern as described above readily and undesirably occurs.
Also, in the apparatus disclosed in Japanese Patent Laid-Open No. 2009-532245, a recovery port for recovering gas is provided in a space between a mold and a substrate so as to depressurize the space therebetween. In this case, the depressurization of the space between the mold and the substrate exerts force such that the mold and the substrate are being close to each other. This force may bring the recovery port and the substrate into contact with each other before gas present in the space between the mold and the substrate is pushed out by bringing the mold into contact with the substrate. When coming into such a state, gas may be entrapped in the space between the mold and the substrate. Consequently, the concave portion of the mold may not be completely filled with an imprint material due to the presence of gas, resulting in the occurrence of defects. Furthermore, a defect from the inclination of the resin pattern formed on the substrate readily occurs due to the deformation of the mold.